My only (extremely minor) concern with using cloth bags for laundry placed inside suitcases among other items pertains to clothes that might smell remarkably bad (e.g. exposed to smoke of any kind, returned from tour of sewage treatment plant, doused in ethanethiol; I googled "world's smelliest liquid" to find this example); I don't want nefarious odors finding their way to my nice smelling clean clothes. In such cases, the cloth laundry bag goes inside a non-permeable plastic bag.

ETA: While this thread topic definitely falls squarely within the waste of time "cube", it has turned out to become far more thought provoking than I could have ever imagined. You guys never fail to provide a wealth of knowledge and insights, no matter how mundane the subject.